I just spotted a couple of typos (probably), one double space, and a couple of places where I'd use commas.

I was expecting your email, Jane; I am glad to receive it. I have one question though: did you decide on your wedding date? Are you marrying the dashing fellow you were with at our high school reunion a few weeks ago? If that's him, you are a lucky girl. He looked so nice and, on top of that, he looked so gentlemanly. Please let me know the details. Bye.

Proper punctuation in emails is to be commended, and you should punctuate them just as you would any other piece of text. For dashes I often use two hyphens (--), as you have. (Not only are proper dashes a pain to enter, but I'm never entirely confident that they will be rendered correctly in whatever system the recipient is using.)

Many "-ly" words are adverbs, but "gentlemanly" is an adjective. The way you've used it is fine -- just as "he looked so handsome" is fine. What you can't say is something like "he looked at me gentlemanly" (intended to mean "in the manner of a gentleman") because this sentence needs an adverb (as in "he looked at me cautiously").